High speed oxyacetylene cutting of a thick steel part and device therefor

ABSTRACT

The invention relates to a method and apparatus for oxygen-cutting thick pieces of steel at high speed. In accordance with the invention an oxygen-cutting torch ( 30 ) held at a predetermined height above the piece ( 1 ) to be cut and a slot torch ( 20 ) comprising at least one blade nozzle ( 25 ) that travels inside the cut slot ( 1.3 ) are moved synchronously. The blade nozzle ( 25 ) emits at least one jet of heating and/or oxygen-cutting fluids through its leading edge to strike the heating edge of the slot where it combines with the jet of oxygen-cutting fluids emitted by the oxygen-cutting torch ( 30 ) to form a leading edge ( 1.4 ) of the slot having a profile in the form of a broken line.

The present invention relates to a method and apparatus foroxygen-cutting pieces of steel, such as slabs, billets, and blooms.

The technical background can be illustrated by document EP-A-0 639 416which describes a two-line oxygen-cutting installation, each linecomprising a moving carriage having a pendulum type oxygen-cuttingtorch. Reference can also be made to document U.S. Pat. No. 2,820,420which describes an oxygen-cutting torch cantilevered out from a carriagethat can be moved horizontally, and to document WO-A-96/20818 whichdescribes a traveling crane supporting a telescopically-extendablevertical working arm.

In general, conventional oxygen-cutting torches are constituted by twomain portions, namely a first portion for delivering fluids (oxygen,fuel gas, cooling liquid), which portion is referred to the torch body,said portion not coming directly into contact with the flame, and anozzle-forming second portion which does come directly into contact withthe flame and which serves to spread and dispense the fluids and toeject the gases (fuel and oxidizer) with specific proportions andcharacteristics specific to fluid mechanics for the purpose of achievingthe desired oxygen-cutting operation.

The person skilled in the art knows that oxygen-cutting nozzles canperform two functions simultaneously: the first function consists inproducing a heating flame by supplying and mixing (outside or inside thenozzle) a fuel gas and an oxidizer gas, such as oxygen, for the purposeof raising the cutting edge zone to very high temperature so as to causethe metal for cutting to enter into spontaneous combustion on arrival ofa separate jet of oxygen. The second function consists in producing anddirecting a specific jet of oxygen on the zone that has already beenraised to spontaneous combustion temperature so as to cut the metal withdesired geometrical characteristics. For this purpose, existingoxygen-cutting nozzles have one or more cutting oxygen ducts, that areoptionally parallel, situated in a common plane (generally orthogonal tothe cutting surface of the piece to be cut), together with a certainnumber of heating ducts which are arranged either concentrically aroundthe cutting jet of oxygen, or else on either side of the traveldirection of the cutting jets of oxygen.

The oxygen-cutting nozzles used in traditional techniques are positionedat a certain distance from the “cutting” surface of the piece forcutting, with the direction of the cutting jet of oxygen generally beingselected to being substantially perpendicular to the cutting surface toimprove effectiveness (if the cutting jet of oxygen is orthogonal to thecutting surface, then the thickness of material that needs to be cutthrough is minimized, thereby enabling the speed of cutting to bemaximized and providing savings in fluid consumption).

In general, all of the oxygen-cutting nozzles presently in use aremounted so as to move relative to the piece for cutting, above and/orbelow said piece, but always outside the cut slot. This constitutes amajor drawback insofar as the cutting jet of oxygen needs to travel aconsiderable distance through the open air between leaving theoxygen-cutting nozzle and striking the surface of the metal to be cut.This drawback naturally increases with increasing thickness of the pieceto be cut, and puts a de facto limit on using oxygen-cutting techniquesto cutting pieces of relatively small thickness only. This drawback alsoapplies to the heating jet which is generally restricted to heating theimpact zone on the surface and/or down to a shallow depth from thesurface of the piece. It is the heat given off by the spontaneouscombustion of the hot metal due to the cutting oxygen that serves togenerate and propagate heat along the cut slot throughout the entirethickness of the piece being cut, thus making it possible to maintainand continue the oxygen-cutting operation by spontaneous combustionusing the cutting oxygen. During the cutting process, the jet ofoxygen-cutting fluids emitted by the oxygen-cutting torch held at adetermined height above the piece forms a slot which passes rightthrough the thickness of the piece that is to be cut. The leading edgeof the slot is then substantially rectilinear and in line with the axisof the oxygen-cutting jet, said line moving progressively during thecutting process at a speed referred to the oxygen-cutting speed, whichspeed corresponds to the speed of travel of the oxygen-cutting torchrelative to the piece to be cut. For a nozzle having given geometricaland fluidic characteristics, the oxygen-cutting speed is a function,amongst other things, of the thickness of the piece to be cut: thegreater the thickness of the piece, the slower the cutting speed becauseof combustion heat and combustion itself propagating along the slot fromits inlet to its outlet by degrees in non-instantaneous manner.

To fill out the state of the art, mention can also be made of variousoxygen-cutting methods that make use of a plurality of torches.

Thus, document U.S. Pat. No. 3,852,126 describes an oxygen-cuttingmethod making use of two torches, a first torch having a vertical axisand a second torch having an oblique axis. That disposition is intendedto enable the two torches to be brought together laterally in adirection extending transversely relative to the trajectory so that thetwo slots overlap in part. Nevertheless, no mention is made of movingthe two torches so close together that their respective slots overlapcompletely, nor is there any mention of inserting one of the torchesinto the slot made by the other.

Document EP-A-0 017 807 describes oxygen-cutting apparatus presenting afirst cutting torch having a vertical axis associated with a secondtorch for trimming purposes carried by a support blade that passes intothe slot, the sole and unique function of the second torch being torectify the edges of the slot on the face of the piece to be cut that isremote from its face facing the torch.

Finally, the technological background is illustrated by documentsJP-A-60 052 985 and U.S. Pat. No. 3,492,552.

Document JP-60 052 985 describes a method of forming an edge with acurved groove by providing for a vertical axis torch to pass in order toobtain a straight cut followed by a torch which is transversely obliquein order to obtain a cut at 45°, and finally followed by a melting torchin order to form the concave edge. Document U.S. Pat. No. 3,492,552describes a numerically-controlled apparatus for positioning a torchrelative to a workpiece.

The invention relates more particularly to oxygen-cutting thick piecesof steel at high speed. It will be understood that existing techniquesprovide performance that is very limited, both as to the thickness ofthe piece that can be cut and as to the speed of oxygen-cutting.

The invention seeks to devise an oxygen-cutting technique that enablesthe above-specified drawbacks and/or limitations to be avoided.

An object of the invention is thus to provide a method and apparatus foroxygen-cutting thick pieces of steel at high speed, being capable ofcutting thick pieces of steel in regular and fast manner regardless ofthe thickness of the piece to be cut. In particular, the looked-fortechnique must be capable of performing splitting operations underconditions that are technically and economically satisfactory.

According to the invention, this problem is solved by a method ofoxygen-cutting a thick piece of steel at high speed in which anoxygen-cutting torch held at a determined height above the piece to becut is moved and in which a slot torch comprising at least one bladenozzle that passes inside the oxygen-cutting slot is also movedsynchronously with the movement of the oxygen-cutting torch, said bladetorch emitting at least one jet of heating and/or oxygen-cutting fluidsvia its leading edge to strike the leading edge of the slot where theycombine with the jet of oxygen-cutting fluids emitted by theoxygen-cutting torch to form a leading edge of the slot having a profilein the form of a broken line.

By using a slot torch acting from inside the oxygen cut slot, theabove-mentioned drawbacks of the jet of heating and/or oxygen-cuttingfluids traveling long distances is avoided, and additionallyoxygen-cutting power is increased by increasing the number ofoxygen-cutting nozzles if it is desired to have very high power in orderto cut through thick pieces, e.g. pieces which are considerably thickerthan 10 centimeters (cm). Depending on circumstances, the slot torch canbe used as an injection nozzle (single or multiple), serving only toproject heating fluids towards the leading edge of the slot.

Preferably, the jet from the oxygen-cutting torch extends in a directionwhich is substantially perpendicular to the corresponding surface of thepiece to be cut, while the jet(s) from the slot torch is/are inclined ata determined acute angle relative to said direction.

Under such circumstances, and advantageously, the slot torch emits aplurality of superposed jets of heating and/or oxygen-cutting fluidsengaging the leading edge of the slot at different acute angles, withthe values of the angles increasing with increasing distance from thesurface of the piece that is engaged by the jet from the oxygen-cuttingtorch. By using a plurality of superposed jets of oxygen-cutting fluidsengaging the same leading edge of the slot at different acute angles,the length of the slot, i.e. the distance between its inlet and itsoutlet is subdivided into a plurality of segments or “oxygen-cuttingsteps” by allocating an oxygen-cutting nozzle having its own specificcharacteristics to each of the segments such that the speed at which thepiece is cut is increased considerably, so as to reach the speedpossible for a single step. This is thus the first occasion on which agenuine slot nozzle has been used within the oxygen cut slot throughoutthe cutting process.

Preferably, the oxygen-cutting torch and the slot torch are movedsynchronously by mounting their associated supports on a common carriagemoving horizontally above the piece to be cut. In particular, theoxygen-cutting and slot torches are movable vertically, the slot torchbeing retractable above the piece to be cut.

Provision can also be made for the slot torch to be set into verticalvibration during at least a portion of the cutting process. Impartingsuch vertical vibration facilitates progress of the slot blade along thecut slot as the blade advances during the cutting process.

The invention also provides apparatus for implementing theabove-specified oxygen-cutting method, the apparatus being remarkable inthat it comprises a horizontally displaceable carriage, said carriagecarrying supports for an oxygen-cutting torch and a slot torch, theoxygen-cutting torch being vertically above the piece to be cut andbeing arranged to emit a substantially vertical jet of oxygen-cuttingfluids, while the slot torch has at least one blade nozzle arranged tomove inside the cut slot and to emit at least one inclined jet ofheating and/or oxygen-cutting fluids from its leading edge.

Preferably, the supports for the oxygen-cutting and slot torches areindividually adjustable in vertical position. In particular, the supportfor the slot torch is suspended from a vertical axis actuator, saidactuator having a stroke enabling the blade nozzle(s) to be raised abovethe piece to be cut.

Provision may optionally be made for the cylinder of the actuatorsupporting the slot torch to be connected to a vibrator capable ofgenerating low amplitude vibration in a vertical direction.

In a particular embodiment, the blade nozzle of the slot torch is asingle nozzle, having a set of internal channels extending obliquelybetween the top facet and the leading edge of said blade nozzle.Naturally, in a variant, provision can be made for nozzles in the formof multiple blades, each being capable of emitting one or more jets ofoxygen-cutting fluids.

In which case it is preferable for the internal channels to be arrangedto form at least one group associated with a single jet of heatingand/or oxygen-cutting fluids so as to enable the cutting oxygen and/orheating gas to be passed together with a cooling fluid. In particular,the blade nozzle has a plurality of groups of internal channels forproducing superposed inclined jets, with the channels in any one groupbeing identically inclined relative to the vertical, and with the angleof inclination increasing from one group to the next going downwards insaid blade nozzle.

When the piece being cut is a continuous casting, it is advantageous toprovide for the carriage supporting the oxygen-cutting and slot torchesto be displaceable transversely to the continuous casting direction,being mounted on a main carriage which moves horizontally above themoving piece in the continuous casting direction, said main carriagehaving means for temporarily connecting it with said moving piece.

Other characteristics and advantages of the invention appear moreclearly in the light of the following description and the accompanyingdrawings relating to particular embodiments, and in which:

FIG. 1 is a diagram showing an installation implementing the high speedoxygen-cutting method of the invention, which method is applied in thiscase to cutting a piece that is being cast continuously, said piecebeing shown in section on a vertical plane contained in the cut slot;

FIGS. 2 and 3 are sections respectively on II—II and III—III of FIG. 1showing more clearly how the oxygen-cutting torch and the slot torch aredisposed respectively during the cutting process;

FIG. 4 is a diagrammatic view showing the slot torch used in the methodof the invention together with the feeder distributors fitted to thebody of the torch, the torch nozzle being a flat nozzle in the form of ablade;

FIGS. 5 and 6 are elevation views showing two different embodiments ofthe blade nozzle of the slot torch, respectively in the form of a singlenozzle emitting a plurality of superposed oblique jets, and in the formof a plurality of complementary nozzles each emitting a single obliquejet;

FIG. 7 is a section view on a much larger scale showing the thick piecewhile it is being cut, and showing the particular shape of the leadingedge of the slot as a broken line made up of segments that result fromusing a blade nozzle that emits superposed jets of heating and/oroxygen-cutting fluids; and

FIG. 8 is an end view of the above-described blade nozzle, while FIG. 9is a section view on IX—IX of FIG. 8 showing more clearly how thechannels inside the blade nozzle are arranged, with this particularexample having three groups of internal channels for the purpose ofproducing superposed inclined jets.

FIGS. 1 to 3 show a piece of steel such as a slab, a billet, or a bloomin the process of being cut by using the high speed oxygen-cuttingmethod of the invention. The piece 1 for cutting has a top surface 1.1and a bottom surface 1.2, and it rests horizontally on rollers 2. Sincethis particular piece is a continuous casting, the piece 1 for cuttingmoves along the rollers 2 in a horizontal direction referenced 101.

In the figures there can be seen apparatus referenced 10 forimplementing the high speed oxygen-cutting method of the invention.

This apparatus comprises firstly a first carriage 11 moving on wheels 12running on a support R, which carriage is referred to as a “tracking”carriage. The carriage 11 moves horizontally over the piece 1 to be cut,and while the cutting method is being implemented, it is evenmechanically linked to said piece by means of a support 15 whichterminates in a gripping device 16. The structure of this temporaryconnection means may naturally vary depending on circumstances, and itwould be equally possible to use magnetic devices or clamp systems thathold onto the piece for cutting via its side facets.

A second carriage 13 is horizontally movable, having wheels 14 that runon rails secured to the bottom of the carriage 11, with the traveldirection referenced 100 of this carriage 13 being perpendicular to thetravel direction of the carriage 11. The second carriage 13 can thus bereferred to as a “transverse” carriage since it travels transversely tothe moving piece 1 in order to cut the piece across its entire width andits entire thickness.

The carriage 13 carries firstly a support 19 for a traditional type ofoxygen-cutting torch 30. This oxygen-cutting torch 30 is disposedvertically above the piece to be cut and it is arranged to emit apowerful and substantially vertical jet referenced 36 of heating andoxygen-cutting fluids. The support 19 is connected to a horizontal plate17 secured to the carriage 13. FIGS. 1 and 3 show the arrangement ofthis support 19 which comprises a column 31 terminated at its bottom endby a collar 29 holding the oxygen-cutting torch 30, which torch can betaken to a desired vertical position which is adjustable and lockable bymeans of a positioning screw 32. Reference 34 designates hoses forfeeding the various oxygen-cutting fluids. The jet 36 emitted by theoxygen-cutting torch 30 thus engages the top portion of the thickness ofthe piece. This portion of the leading edge of the slot is thusessentially vertical.

In accordance with an important characteristic of the invention, thecarriage 13 also has a support 18 for a slot torch 20. The slot torch 20comprises a torch body 23 that is extended downwards by a blade nozzle25 which is arranged to move inside the cut slot referenced 1.3, andwhich is arranged to emit at least one inclined jet 26 of heating and/oroxygen-cutting fluids through its front edge. In FIG. 1, arrow 102presents the direction of advance of the oxygen-cutting process, and itcan be seen that the blade nozzle 25 moves inside the slot 1.3, with thejets of heating and/or oxygen-cutting fluids that it emits thus engagingthe remaining portion of the leading edge of the slot, which edge isreferenced 1.4. The body 23 of the slot torch 20 is secured to a column22 which is connected in this case to the rod 27 of an actuator 21, andspecifically a pneumatic actuator. The axis of the actuator 21 isvertical and its cylinder is bolted to the horizontal plate 17.

Thus, the cutting torch 30 and the slot torch 20 are connected via theirassociated supports 19 and 18 to a common carriage 13 which moveshorizontally above the piece to be cut, this common mount thus ensuringthat both torches move synchronously during the cutting process. The useof an actuator also makes it possible to adjust the vertical position ofthe slot torch 20, i.e. the precise position of the blade nozzle 27 sothat its jet(s) 26 is/are directed against particular points of theleading edge of the slot with great accuracy. The stroke of the actuatoris preferably selected to be such that it is possible to retract theslot torch 20 above the piece when this torch is not in use. Theactuator thus enables the blade nozzle(s) 25 to be raised above thepiece that is to be cut.

A vibrator 28 is also shown mounted at the top of the cylinder of theactuator 21 supporting the slot torch 20, said vibrator being arrangedto generate small-amplitude vibration in a vertical direction. Suchvibration makes it easier for the slot nozzle 25 to move inside the slot13 during the cutting process. As an indication, the amplitude of thevibration can be about 1 millimeter (mm) to 2 mm. The body 23 of theslot torch 20 is also fitted with a plurality of hoses 24 serving tofeed the various fluids concerned.

Thus, and in accordance with an essential characteristic of the methodof the invention, the oxygen-cutting torch 30 and the slot torch 20 aremoved synchronously, the slot torch having at least one blade nozzle 25traveling actually inside the cut slot 1.3, said blade nozzle emittingat least one jet 26 of heating and/or oxygen-cutting fluids through itsleading edge so as to strike the leading edge 1.4 of the slot where itcombines with the jet 36 of heating and oxygen-cutting fluids emitted bythe oxygen-cutting torch 30 so as to form a leading edge 1.4 of the slothaving a profile in the form of a broken line.

It should be observed in FIG. 1 that the jet 36 of the oxygen-cuttingtorch 30 extends in a direction which is substantially perpendicular tothe corresponding surface 1.1 of the piece to be cut, whereas the jet(s)26 of the slot torch 20 is/are inclined at a determined acute anglerelative to said direction. The importance of the inclination of theslot torch jet is described in greater detail below, in particular withreference to FIGS. 8 and 9.

The blade nozzle 25 of the slot torch 20 may be constituted as a singlepart as shown in FIG. 5 or as a plurality of parts as shown in FIG. 6.

In FIG. 5, the blade nozzle 25 has a set of internal channels 60.1,60.2, and 60.3 which extend obliquely between the top facet 54 and aleading edge 55 of said blade nozzle. The associated inlets arereferenced 56.1, 56.2, and 56.3, while the jets of heating andoxygen-cutting fluids that leave via the leading edge 55 of the blade 25are referenced 26.1, 26.2, and 26.3. The associated outlet anglesreferenced a1, a2, and a3 are preferably different, intersectingdownwards away from the blade nozzle 25.

In FIG. 6 there is shown a variant in which the blade nozzle 25 is madeup of a plurality of parts, i.e. it comprises three blade nozzlesubassemblies 25.1, 25.2, and 25.3. Each subassembly has its own fluidinlets respectively referenced 56.1, 56.2, and 56.3, and its own outletsfor heating and/or oxygen-cutting fluids in the form of oblique jetsrespectively referenced 26.1, 26.2, and 26.3. The internal channels60.1, 60.2, and 60.3 are then arranged accordingly inside the thicknessof each of these three components making up the blade nozzle 25.

It will be understood that the number of internal channels used foremitting superposed inclined jets will vary in practice as a function ofthe operating conditions encountered.

The views of FIGS. 5 and 6 are clearly diagrammatic insofar as each ofthe channels 60.1, 60.2, and 60.3 is in fact made up of a group ofchannels associated with the various fluids making up any one outletjet. Thus, there are channels for heating gas, for cutting oxygen, andfor cooling fluid. If it is desired to use the slot torch as a single ormultiple injection nozzle, then the fluids that are ejected andprojected against the leading edge of the slot are constituted solely byheating fluids.

FIG. 4 shows more clearly how the body 23 of the slot torch 20 isarranged for fluid feed purposes. The outline of the body of the torch23 is represented by a chain-dotted line, and it includes a plurality offeeder distributors, each associated with a different one of the fluidsinvolved. Reference 60 designates the various internal channels providedin the thickness of the head of the blade nozzle 25. In order to feedthese various channels, there is a first distributor 40 having an inlet41 for cutting oxygen, which oxygen is delivered via a tube 43, adistributor 44 for feeding heating gas having inlets 45 and 46corresponding to fuel gas and to oxygen, these gases being delivered viaassociated tubes 47 and 48, and finally there is a distributor 49 forfeeding cooling fluid, e.g. water, having a water inlet 50 and a wateroutlet 51, connections being provided via associated respective tubes 52and 53.

It should be observed that during the cutting process the blade nozzle25 moves inside the cut slot, thus producing a non-negligible advantagein terms of heating insofar as the oxygen-cutting fluids are naturallypreheated, with this being particularly advantageous for the cuttingoxygen. The cutting oxygen duct is heated by heat from theoxygen-cutting operations, and also by the radiant heat from the cutpiece if it is still hot, as is the case for continuously cast steelslabs. This heat is transferred to the oxygen-cutting fluids which actto cool the blade and to exchange heat, thus enabling heat to bedelivered to the combustion which requires it.

As mentioned above, it is the combination of the jets from theoxygen-cutting torch and from the slot torch that enables oxygen-cuttingto be performed at high speed, even when the piece to be cut is verythick.

The inclination of the jet(s) 26 from the slot torch 20 has the effectof forming a leading edge 1.4 in the slot whose profile follows a brokenline. If the slot torch 20 has a blade nozzle emitting a single jet 26of oxygen-cutting fluid, then the leading edge 1.4 of the slot is madeup of two segments only, comprising a vertical segment associated withthe jet 36 from the oxygen-cutting torch 30, and an oblique segmentassociated with the jet 26 from the slot torch 20. Nevertheless, inpractice, it is advantageous to provide a plurality of superposed jets,and one such example is shown in FIG. 7.

Specifically, the blade nozzle 25 has three groups of internal channelsfor emitting three superposed jets 26.1, 26.2, and 26.3 ofoxygen-cutting fluids. Each of these jets gives an associated obliqueshape to the leading edge 1.4 of the slot. In this case, the zonereferenced AB belongs to the outside oxygen-cutting torch 30 whose jet36 is perpendicular to the cutting surface 1.1. The other three segmentsreferenced BC, CD, and DE correspond respectively to the inclined jets26.1, 26.2, and 26.3 emitted by the blade nozzle 25 of the slot torch20. The corresponding angles of inclination relative to the vertical arereferenced a1, a2, and a3. The broken line ABCDE, constituted in thiscase by four segments, forms the leading edge 1.4 of the oxygen-cuttingslot. In the example shown in FIG. 7, the three zones associated withthe three nozzle cutting steps of the blade nozzle 25, i.e. BC, CD, andDE are substantially equal in length. In contrast, the zone ABassociated with the outside torch is a little longer, because of thedesired level of power given to the oxygen-cutting torch 30.Nevertheless, it should be understood that this distribution can bemodulated as a function of circumstances, and the angles of inclinationa1, a2, and a3 are selected accordingly so as to obtain zones having thedesired lengths. By way of example, more importance could be given tothe last step by increasing the angle a3 so as to increase the length ofthe segment DE.

It will thus be understood that each individual oxygen-cutting fluid jetis required to cut only a portion of the thickness of the piece that isto be cut, i.e. only one of the four above-mentioned segments, with thissharing of the work making it possible specifically to achieve very highoxygen-cutting speeds in spite of the great thickness of the piece to becut.

The way in which the internal channels in the blade nozzle 25 arearranged in order to deliver three superposed jets 26.1, 26.2, and 26.3of heating and/or oxygen-cutting fluids will be better understood onreferring to FIGS. 8 and 9.

In FIG. 9 it can be seen that the blade nozzle 25 of the slot torch, asingle nozzle in this example, presents a set of internal channelscomprising a plurality of groups, each being associated with arespective jet of heating or oxygen-cutting fluids. Specifically, anembodiment is shown that has three groups of internal channelsrespectively referenced 60.1, 60.2, and 60.3. Each of these groupsitself comprises a plurality of inclined internal channels, with all thechannels in any one group having the same slope.

Individual references are given to the internal channels of the firstgroup 60.1 of channels, it being understood that this group whichconstitutes the first step is subsequently repeated, but with adifferent slope each time.

Thus, there can be seen in succession going away from the outlet edge55: a channel 60.11 associated with the cooling water inlet; a channel60.12 associated with the cooling water outlet; a channel 60.13associated with the heating fuel gas inlet; a channel 60.14 associatedwith the heating oxygen inlet (it should be observed that these twochannels 60.13 and 60.14 join together upstream from the outlet so as toopen out via a single channel); and two channels 60.15 and 60.16corresponding to the cutting oxygen outlet. These six channels 60.11 to60.16 form a single oxygen-cutting “step”, which step is characterizedby its angle of inclination a1. The other groups of channels 60.2 and60.3 are arranged in analogous manner, but their respective inclinationsa2 and a3 increase progressively going downwards through the bladenozzle 25.

FIG. 8 shows the associated outlet orifices in the leading edge 55 ofthe blade nozzle 25: for each group of channels associated with aparticular oxygen-cutting step, there are to be found in successiongoing downwards: an orifice 61.11 associated with the outlet of heatinggas; and two orifices 61.12 and 61.13 associated with delivering cuttingoxygen.

As just described, all of the oxygen-cutting steps can be incorporatedin a single oxygen-cutting blade, or else each oxygen-cutting step canbe constituted by an independent blade, as mentioned previously.

The simultaneous action of the oxygen-cutting step at differentindividual angles of inclination serves to share the total length of theleading edge of the oxygen-cutting slot amongst the variousoxygen-cutting steps, preferably in uniform manner or in a manner thatis proportional to the power of the nozzle of each oxygen-cutting step,thereby enabling the time required to cut through the total thickness tobe reduced to the time required to cut through the smaller thicknesstreated by the nozzle of each individual oxygen-cutting step.

As mentioned above, the open channels of one or more of the groups ofchannels could be used solely to project heating fluids towards theheating edge of the slot. It is thus possible to provide one or moreinjection nozzles that are received directly in the slot.

Finally, in order to facilitate manufacture and connection of such amultiple-channel blade, it is possible to make use of bent tubes havingupstream ends of round section (for ease of connection to a feederdistributor), with the remainder thereof being of flat section (tominimize size in a lateral direction).

A method and apparatus are thus provided for high speed oxygen-cuttingthat enables thick pieces of steel to be cut, in particular pieces thatare considerably greater than 10 cm in thickness. The method and theapparatus of the invention are naturally equally applicable to a piecethat is stationary or to a piece that is being cast continuously.

The invention is not limited to the embodiments described above, but onthe contrary covers any variant using equivalent means to reproduce theessential characteristics specified above.

What is claimed is:
 1. A method of oxygen-cutting a piece of steel athigh speed comprising: moving an oxygen-cutting torch, which ismaintained at a height above the piece to be cut and cutting a slotwithin said piece; disposing a slot torch (20) comprising at least oneblade nozzle (25) inside the slot (1.3); moving the slot torch (20)synchronously with the movement of the oxygen cutting torch (30) andemitting at least one jet (26) of heating and/or oxygen cutting fluidsfrom said at least one blade nozzle, wherein the at least one jet ofheating and/or oxygen cuffing fluids from the blade nozzles strike aleading edge (1.4) of the slot and combine with a jet (36) of the oxygencutting fluids emitted by the oxygen cutting torch (30) to form aleading edge (1.4) of the slot.
 2. A method according to claim 1,wherein the jet (36) from the oxygen-cutting torch (30) extends in adirection which is substantially perpendicular to the correspondingsurface (1.1) of the piece to be cut, while the jet(s) (26) from theslot torch (20) is/are inclined at a determined acute angle relative tosaid direction.
 3. A method according to claim 2, wherein the slot torch(20) emits a plurality of superposed jets (26.1, 26.2, 26.3) of heatingand/or oxygen-cutting fluids engaging the leading edge (1.4) of the slotat different acute angles, with the values of the angles increasing withincreasing distance from the surface (1.1) of the piece that is engagedby the jet (36) from the oxygen-cutting torch (30).
 4. A methodaccording to claim 1, wherein the oxygen-cutting torch (30) and the slottorch (20) are moved synchronously by mounting associated supports (19;18) on a common carriage (13) moving horizontally above the piece to becut.
 5. A method according to claim 1, wherein the oxygen-cutting andslot torches (30; 20) are movable vertically, the slot torch (20) beingretractable above the piece to be cut.
 6. A method according to claim 1,wherein the slot torch (30) is set into vertical vibration during atleast a portion of the cutting process.
 7. Apparatus for implementingthe oxygen-cutting of a work piece, comprising: an oxygen cutting torch(30); a slot torch (20); a horizontally displaceable carriage (13), saidcarriage carrying supports (19; 18) for said oxygen-cutting torch (30)and said slot torch (20), the oxygen-cutting torch (30) being verticallyabove the work piece and being arranged to emit a substantially verticaljet (36) of oxygen-cutting fluids, while the slot torch (20) has atleast one blade nozzle (25) arranged to move inside the cut slot (1.3)and to emit at least one inclined jet (26) of heating and/oroxygen-cuffing fluids from its leading edge.
 8. Apparatus according toclaim 7, wherein the supports (19; 18) for the oxygen-cutting and slottorches (30; 20) are individually adjustable in vertical position. 9.Apparatus according to claim 8, wherein the support (18) for the slottorch (20) is suspended from a vertical axis actuator 921), saidactuator having a stroke enabling the blade nozzle(s) (25) to be raisedabove the piece to be cut.
 10. Apparatus according to claim 9, whereinthe cylinder of the actuator (21) supporting the slot torch (20) isconnected to a vibrator (28) capable of generating low amplitudevibration in a vertical direction.
 11. Apparatus according to claim 7,wherein the blade nozzle (25) of the slot torch (20) is a single nozzle,having a set of internal channels (60.1, 60.2, 60.3) extending obliquelybetween a top facet (54) and a leading edge (55) of said blade nozzle.12. Apparatus according to claim 11, wherein the internal channels(60.1, 60.2, 60.3) are arranged to form at least one group associatedwith a single jet of heating and/or oxygen-cutting fluids so as toenable the cutting oxygen and/or heating gas to be passed together witha cooling fluid.
 13. Apparatus according to claim 12, wherein the bladenozzle (25) has a plurality of groups of internal channels (60.1, 60.2,60.3) for producing superposed inclined jets (26.1, 26.2, 26.3), withthe channels in any one group being identically inclined relative to thevertical, and with the angle of inclination increasing from one group tothe next going downwards in said blade nozzle.
 14. Apparatus accordingto claim 7, for oxygen-cutting a piece that is being cast continuously,wherein the carriage (13) supporting the oxygen-cutting and slot torches(30; 20) is displaceable transversely to the continuous castingdirection (101), being mounted on a main carriage (11) which moveshorizontally above the moving piece in the continuous casting direction,said main carriage having means (15, 16) for temporarily connecting itwith said moving piece.